docs: def simple_clip_matrix(scale, znear, zfar, aspectratio=1.0):
      '''Given the parameters for a frustum returns a 4x4 perspective
      projection matrix 
      
      Parameters:
        float scale: 
        float znear,zfar: near/far plane z, float
  
      Return: a 4x4 perspective matrix
      '''
      m = numpy.zeros((4,4))
      m[0,0] = scale/aspectratio
      m[1,1] = scale
      m[2,2] = (zfar + znear) / (znear - zfar)
      m[2,3] = 2*zfar*znear / (znear - zfar)
      m[3,2] = -1
  
      return m